Yarn tensioning and severing mechanism for circular knitting machines



March 5, 1963 v H BUTLER EI'AL 3,079,779

YARN TENSICNING AND SEVERING MECHANISM FOR CIRCULAR KNITTING MACHINES Filed Dec. 6, 1956 5 Sheets-Sheet 1 FIG.].

' a l 86 x 90 FIG. 2.

INVENTORS VAUGHN H. BUTLER AARON BURLESON ATTORNEYS March 5., 1963 v. H. BUTLER EI'AL 3,079,779

YARN TENSIONING AND SEVERING MECHANISM FOR CIRCULAR KNITTING MACHINES Filed Dec. 6, 1956 5 Sh he 2 FIG.5.

u mm mm INVENTORS m 0A 30A VAUGHN H.BUTLER AARON BURLESON UMZ 941% ATTORNEYS March 1963 v. H. BUTLER EI'AL 3,079,779

YARN TENSIONING AND SEVERING MECHANISM FOR CIRCULAR KNITTING MACHINES Filed Dec. 6, 1956 5 hee she 3 FIG. 8.

30 use 22 4 a: 2 I96 I O 1 I98 uo I00 I06 INVENTORS VAUGHN H.8UTLER AARON BURLESON ATTORNEYS March 1963 v. H. BUTLER EI'AL 3,07

YARN TENSIONING AND SEVERING MECHANISM FOR CIRCULAR KNITTING MACHINES Filed Dec. 6, 1956 5 Sheets-Sheet 4 INVENTORS nm N VAUGHN H.BUTLER AARON BURLESON iz MM v idjwtldd ATTORNEYS March 5, 1963 v. H. BUTLER EI'AL 3,079,779

YARN TENSIONING AND SEVERING MECHANISM FOR CIRCULAR KNITTING MACHINES Filed D80. 6, 1956 5 Sheets-Sheet 5 FIGJI.

INVENTORS VAUGHN H.8UTLER AARON BURLESON United States Patent 3,679,779 YARN TENSEGIJENG AND SEVERlNiG MEEHANESM FUR QIRSULAR KNETTKPJG MAQHINES Vaughn H. Butler, Harriman, Tenn, and Aaron Eurleson,

Burlington, N.'J., assignors, by mesne assignments, to

'lg e Gordon Qonipany, ldinston-Salezn, NIL, a partner- Filed Bee. 6, 1956, Ser. No. 626,6?1 4- Claims. (6i. 66-14%) This invention relates to circular knitting machines, and in particular to improved tears and methods for handling and severing yarns on the dial caps thereof.

in the knitting of tubular articles such as seamless hosiery, frequent yarn changes are commonly effected in the course of the knitting cycle. In the case of hosiery, for example, the welt and leg may be knitted of different yarns, and heavier yarns are frequently employed in the heel and toe. At each yarn change an inactive yarn is dropped into the needles for knitting and an active yarn is withdrawn from the knitting a few needles later. Two yarns extend from the resultant yarn lap, and these are commonly severed so as to be an inch or two in length. Since yarn ends of such length are easily noticeable and unsightly, they must be clipped, and this is usually done individually and manually during inspection. The yarn ends are clipped down LO a length of /4 or /8, which is commercially satisfactory. The clipping operation is obviously time consuming and expensive, and exposes the stockings to possibility of damage.

A principal object of the present invention is the provision of novel means and methods for holding and tensioning yarns over the dial cap of the machine by means of suction, whereby better and more reliable control of the yarns is effected.

The yarns so tensioned may be automatically severed close to the fabric during yarn changes, with such reliability as to eliminate subsequent inspection and clipping of free ends. Additionally, the improved mode of tensioning assures positive yarn laps, principally by eifectively holding and tensioning inactive yarns prior to and during insertion into the fabric. Relate-d objects are to provide means and methods for positively picking up and removing cut ends severed from newly inserted yarns, and to pick up and engage the ends of newly withdrawn yarns, and hold them in readiness for reinsertion.

A particular object of the invention is the provision of a novel combination suction and clamping device for circular knitting machines, adapted to facilitate automatic severing of newly inserted yarns close to the fabric being knitted.

Another object of ti e invention is to provide novel yarn severing means and methods for circular knitting ma chines, involving the use of a resistance wire heated to red heat prior to and during yarn changes and adapted to sever yarns on contact by the local application of inense heat thereto, close to the fabric being knitted. Further objects will be in part evident and in part pointed out hereinafter.

The invention and the novel features thereof may best be made clear from the following description and the ac companying drawings in which:

FIGURE 1 is a side elevational view of a preferred embodiment of the invention, illustrating a combination suction and clamping device in operative association with related parts of the knitting machine;

FlGURE 2 is a vertical sectional view through the yarn tensioning mechanism of FIGURE 1;

FIGURE 3 is a view taken on the line 3-3 of FIG- URE 2;

FIGURE 4 is a view taken on the line 44 of FIG- URE 2;

FIGURE 5 is a plan view illustrating the operation of the device of the previous figures during insertion of an inactive yarn into the knitting;

FIGURE 6 is a similar view illustrating the operation during withdrawal of an active yarn from the knitting;

FlGURE 7 is a diagrammatic illustration of the electrical circuit of the invention;

FIGURE 8 is a side elevational view of a simplified embodiment of the invention, utilizing suction as the sole means of holding and tensioniug the yarns;

FIGURE 9 is a plan View illustrating the operation of the FlGURE 8 embodiment during yarn insertion;

FIGURE 10 is a similar view illustrating the operation of the FIGURE 8 embodiment during yarn withdrawal, and

FIGURE 11 is an elevational view of the pneumatic system of the invention.

Referring to the drawings in detail, FIGURE 1 illustrates a portion of a conventional seamless hosiery machine, such as a 400 needle Model KN Scott & Williams machine. As shown, the latch ring 2i;- encloses the knitting station indicated generally as 22, the latter being provided with a yarn guide plate 24 and a plurality of yarn fingers 26 which are individually retractable and function as interchangeable yarn feeds. The yarn fingers are pivotally mounted at 28, and actuated in conventional manor by thrust bars maintained in contact with the main pattern drum of the machine. Knitting yarns 3i} pass through eyes in the guide plate 24 and through the ends of the yarn fingers 26, the active yarn extending from its yarn finger to the adjacent knitting needles 32. The needles 32 are independently mounted in the rotating cylinder of the machine,and extend thereabove adjacent the periphery of t re dial and dial cap 34. The usual dial drive pinion 36 is mounted on the upper end of dial drive shaft 38 (FIGURE 5), which serves to effect rotation of the transfer jacks to in synchronism with the cylinder.

On the dial cap, slightly beyond the position of the yarn fingers in the direction of cylinder rotation (counterclockwise in FIGURE 5), is mounted a guide tongue 42. Thcreoeyond, at a position spaced singularly from the knitting station 22 by about the conventionrd clamp and shear mechanism of the dial cap is replaced in accordance with the present invention with a novel yarn tensioning device indicated generally as 44. As best shown in FIGURE 2, the tensioning device 44 com prises a block or housing 46 mounted a short distance, such as or above the dial ca as by means of screws 43 engaging and extending through the housing and into the dial cap. As est shown in FIGURE 2, a bore 54; extends vertically through the housing 46, the bore having a sleeve 52 slidably mounted therein. The sleeve 52 is closed at its upper end 5 to define an internal chamber 56, and extends upwardly beyond the housing as a solid rod portion 58. The sleeve 52 is provided with diametrically opposed vertically extended slots 65 and 62 opening into the internal chamber thereof. A pressure conduit 64 extends through the housing 45, being secured in place as by screw 66, and is formed into a nozzle end 63 extending through the sleeve slot 68 and terminating a short distance inwardly thereot. An exhaust conduit 7:) extends through the housing and into the opposite sleeve slot 62, the exhaust conduit being suitably retained in place as by the bracket 72 extending therefrom to a position over the top of the hous ing, where it is anchored by screw 74. As will be understood, limited movement of the sleeve 52 in vertical direction relative to the housing 4-6 and conduits 6d and 70 is permitted by the extended slots so and 62.

A vertical slot 76 in the upper end of rod portion 58 .3 encloses an end of lever 78, these elements being pi-votally engaged by a pin 89 extending therethrough. The lever 78 is pivoted approximately at its center 82, and the opposite end thereof is engaged by an actuating rod 84, which extends upwardly through a bore in the extension 86 carried on the end of the operatingtlever S8. The actuating rod 34 is flexibly engaged to the operating lever extension 85 by, its lock collars 9i) and spring 92, whereby vertical movement of the operating lever acting through lever 78 serves to move .the' sleeve 'SZinto and out of contact with the dial cap (Edi-the spring 92 accommodating over travel of the operating lever. .The

connected byrod 174 to a bellcrank 176, pivotedat .178

' described in connection with FIGURES 1, 5, 6, 7 and 1 1.

operating lever 88 is actuated in conventional manner by a thrust'rod maintained in engagement with a cam on the main drum, and may conveniently be the standand operating lever provided to operate the usual clamp and shear mechanism.

Beyond the yarn tensioning device 44, and angularly spaced therefrom in the direction of cylinder rotation approximately 90, a novel yarn severing means 189 may be mounted on the dial cap. As shown in FIGURES 1 and 5, the yarn severing means comprises an insulating block 1ii2 provided with side sockets 1194. A short length of electrical resistance wire 1.06, which may be nickelchromium alloy, platinum or the like, extends between the sockets 164, being retained therein in firm electrical contact by set screws 1113. The resistance wire 106 is formed into a generally vertically extending leading section 110 disposed closely adjacent the path of the needles 3.2, preferably about therefrom, and the upper surface of the dial cap adjacent the severing means is formed into a guide channel 112 adapted to direct yarns slide ing over the dial cap into contact with the wire leading section 1.10. Connector posts 114 are provided on the inner end of the insulating block 102101 the attachment of electrical conductors 116, the connector p'osts being electrically connected through the block 102 to the sockets 134, as will be understood.

As shown in FIGURE 7, current is supplied to the conductors 116 and resistance wire 1&6 by a transformer 113. The transformer 118 is powered by a source12t). through a switch 122, preferably of the Micro switch type. A centrifugal switch 124 may be provided in series with the switch 122, this switch being engaged, as:.by its gear 126, to any convenient element of theme-chine which moves constantly while the machine is in opera tion. 'Ihe centrifugal switch, for example, maybe'driw. ingly engaged to the segment drive gear 128, and a manually operated switch 13-3 bypassing the centrifugal'switch may b'eprovidcd for testing purposes.

The switch122 .is conveniently mounted as by bracket 132 on a frame element .134 of the machine, and .is normally maintained open by downward pressure of an arm 1136 fixed to the upper end of the conventional'stop motion actuating rod 138 of the machine. The stop motion actuating rod is vertically displaced, as is well known, by a link 14?? extending from the pawl 142,'which is disposed over the chain ratchet andthe machine chain 144-. The chain 144 is provided at intervals with lugs 14,6 adapted to elevate the pawl 142, and for a purpose presently apparent each chain 148 preceding each chain lug 145 which corresponds to a yarn change is provided with a low cam 150, adapted to elevate the pawl 142, actuating rod 133 and arm 136 or" the latter very slightly, sufficient merely to permit switch 122 to close.

The invention also comprises a pneumatic system, which is illustrated in FIGURE 11. As there shown, a pressure air line 169 leads to an air valve 162 suitably mounted on the machine. The valve outlet discharges into a small reservoir 164, which in turn communicates with a pressure line such as flexible hose lfioiconnected to the pressure conduit .64 of the yarn tensio ning device n c ua l k 63b pi t l y m n ed at 1 an disea d acent nd, i al gnme t w th theval stem 172 of valve 162. The outer end of link 168 is Referring initially toYFIGURE 5, it may be assumed that the machine is operating in normal round-and-round' knitting, as would be the case in knitting a stocking welt. The yarn finger 26A is illustrated in active position, feeding yarn 30A into the needles 32 for knitting. The yarn finger 2613, in common with the other yarn fingers illustrated, is up in inactiveposition, and the yarn 3013 extends there from under guide tongue 42, into they open bottom end of sleeve 52 of the tensioning device 44, and intothe, exhaust conduit 70 thereof;

Referring next to FIGURE 7, the pawl 142is during straightknitting in lowermost position, as are also link 140and the stop motion actuating rod 138, whereby the arm 136 engages the switch 122 and maintains this switch open, so that no current passes to the transformer 118 and the resistance wire 106 of theyarn severing means 100. The machine beingin operation, it may be noted that the segment drive gear 128is rotating, thereby-rotating'the centrifugal switch 124 and maintaining this switch closed. i i i A .While straight knitting of the yarn 30A proceeds, the bell'crank 176 rides a high portion of the ring cam 182 (see FIGURE 11), ther'eby disposing the actuating link 168 in the position illustrated, out of contact with the stern 172 of the air'va'lve 162, whereby the valve is in normally closed position. The, operating lever 88( FIG- URE l) and the ajs'sociatedactuating rodisare in down position, "so that the lever 78' maintains th'ei's'leeve 52 in elevated position as permitted by 'its' slotsotl an d 62. In such elevated position,'the lower edge 'of.sleeve"52 is substantially at the'level of the lower sur'facefof housing, or' about A to A" above the 'dial cap. This repre sents the relationship of the parts while straight knitting proceeds. i

i As the machine approaches a yarn change, a chain lug 146' corresponding to the yarn jchange approaches the pawl 142. The preceding low cam 150 .passesunder the pawl 1 42, lifting the pawl, the rod 138 and its arm 136 sufficiently to permit switch 122 toclose; This permits a low voltage, for example two voltsQhigh 'amper age'current to flow through the resistance wire 1106, which immediately begins to heat up. Since it is desired thatthe resistance wire be at red heat during the yarn change, the lowca-m 150 provides the required preliminary heat up time. If'necessary, two or more chain links 148 preceding each chain lug 146 correspondingto a y rnch'ange may-be provided with low "cams 150, to provide adequate heat up-time; As will be evident, should the machine be stoppedwhile the switch 122 is closed by a cam 150.01- a lug 146, the centrifu'ga'l switch 124 will come to rest and open, thereby cutting 011 the current flow through resistance wire 106. v

As the machine goes into the yarn change, ajjogof the main drum permits the bell crank 176 (FIGURE 11) to drop into a low portion of the associated ring cam 182. The spring 13% rotates .the bell crank the permitted distance, and through rod 174 rotates the actuating link 168 into contact with stem 172 of valve 162, and displaces the valve stem inwardly to open the air valve. High pressure air immediately flows into reservoir 164 and through flexible hose 165 into the pressure conduit 64 of the 'tensioning device 44. The .high pressure air flow enters the chamber 56,01 sleeve 52 through nozzle end 68, which 'is directed'at the opposite open end of exhaust conduit .79. :Aswill, be understood, the pressure conduit 64, sleeve chamber 56 and exhaust conduit 70 together constitute a continuous air path or conduit for the airflow. The high velocity air flow through the chamber 56 efiects an aspirating action, creating a suction in the chamber 56 and causing air flow into the open bottom end thereof. The free end of the inactive yarn 33B is engaged by this air flow into the chamber 56, and by the high velocity flow into the exhaust conduit 7%, and thereby drawn taut against the restraining inlluence of guide tongue 42, yarn finger 26B, guide plate 24-, and the conventional yarn tensioning and feeding elements of the machine, and efiec 'vely tensioned.

Substantially simultaneously, the yarn finger 26B is dropped to active position, whereby the yarn 3 3B passes etween the needles 32 and is taken thereby. The positive and effective tensioning of the inactive yarn as it is dropped into the knitting, it is found, assures that the inactive yarn is taken by the needles at the desired point, thereby assuring positive yarn laps.

Referring to FIGURE 5, the newly inserted yarn is carried by the first needle to knit in counterclockwise direction. The first needle to knit is indicated as 32, and initially carries the yarn 393 to the position illustrated as 3GB. In movement from initial knitting position to the position 393, the free end of the newly activated yarn is partially drawn out from under the guide tongue 4-2. As the distance from the needle 32' to the sleeve 52 decreases, the free end of the yarn 3GB is drawn up into sleeve 52 and into the exhaust conduit '76 of the yarn tensioning device by air movement, whereby the slaclr is taken up and tension on the free end is preserved.

As the first needle to knit 32' reaches a position adjacent the yarn tensioning device, the free yarn end as sumes the position 3913', the tensioning device functioning as previously described to take up the slack therein and maintain effective tension on the yarn end. At this moment, preferably, the operating lever is elevated by drum movement, elevating the actuating rod 8 to rotate the lever 73 and move the sleeve 52 downwardly into contact with the dial cap, that is to the relative position illustrated in FIGURE 2, whereby the yarn 3GB is firmly clamped between the lover edge of the sleeve 52 and the upper surface of the dial cap. As the yarn is carried by the first needle to knit 32' successively to the positions 3153' and 35 3 of FIGURE 5, as will be understood, the needle 32 must draw the free yarn end out from under the sleeve 52, against the restraining influence of air movement in the chamber 56 and into exhaust conduit 79, and also against the frictional engagement of the yarn between the sleeve and the dial cup. In this manner, the free yarn end is controlled and hinhly tensioned in positive manner during this portion of the yarn change cycle.

When the tensioned yarn end is carried by the needle 32' to the position 333'", it is carried into contact with the leading section 119 of resistance wire tea, the dial cap guide channel 112 assuring the desired alignment. The resistance wire 1% is by this time at red heat, approximately 1,590 B, and the yarn end is severed on contact by the local application of intense heat thereto. The resistance wire severs yarns of nylon, cotton and other fibers with equal facility and reliability, and due to its positional relationship and to the positive control of the travelling yarn invariably severs the yarn within about /4 inch of the fabric.

After the needle 32 passes the yarn severing means 1%, the operative lug 145 passes from under the pawl 142, permitting the pawl 142 and the associated stop motion actuating rod 133 to drop, whereby the rod arm 135 engages and opens the switch 122. This cuts oif the current from the resistance wire 1%, which then cools and remains cool until immediately prior to the next yarn change. Substantially simultaneously, the operating lever 33 is caused to drop, rocking the lever 73 and elevating the sleeve 52 to its up position, releasing the severed yarn end from frictional engagement.

Also, the bell crank 176 is pivoted by movement of ring cam 182, and displaced to the relative relationship illustrated in FIGURE 11. This movement of the bell crank 176 displaces the actuating link 168 out of contact with the stem of air valve 162, and permits the valve to close. The pressure air in reservoir 164 maintains pressure air flow through the flexible hose 166 and the yarn tensioning device for a brief interval of time after the valve 162 is closed. This assures temporary maintenance of suction in the chamber 56 and air flow through the exhaust conduit of the yarn tensioning device, which is effective to remove the severed end of the yarn 393 through the exhaust conduit 70 of the tensioning device. A screen receptacle may be provided on the far end of the exhaust conduit 79, to retain these severed ends.

The foregoing describes the operation in connection with the newly inserted yarn 30B. Substantially concurrently, as will be understood, the yarn SllA is removed from active knittin The active yarn finger 26A is elevated to inactive position a brief interval of time after the yarn finger 26B is dropped into knitting position, this interval of nine corresponding to the passage of, for example, eight needles. Referring to FIGURE 6, it will be seen that the yarn 38A is carried by the last needle 32" to take the yarn away from the yarn finger 26A, being drawn by the needle 32" through the yarn finger and the conventional yarn feeding and tensioning means of the machine. The yarn is drawn initially after witl1- drawal to the position 36A, at which position it begins to pass under the guide tongue 42. As the last needle to knit 32" proceeds around the dial cap, the yarn is extended to the position 3 3A" illustrated, at which position it engages the outside surface of the sleeve 52, then in down position, and wraps around the sleeve or perhaps is drawn thereunder to some degree. The yarn StlA is subsequently extended to the illustrated position 3llA, in which position it is drawn into contact with the leading section 11% of the resistance wire 1M, and severed close to the fabric in the manner described in connection with the newly inserted yarn. In the case or" the yarn 359A being withdrawn from the knitting, the suction and frictional eifect of the yarn tensioning device thereon appear to be minor, but it has been found that the yarn is invariably effectively tensioned by the yarn feeding device, and the combined resistance of its yarn finger, the guide tongue 42 and the yarn tensioning device 44. The opening of the circuit to the resistance wire 1% may be timed to coincide with the arrival of the yarn being withdrawn thereat, or to occur shortly thereafter. Upon the elevation of the sleeve 52, as previously described, the severed end of yarn 30A is sucked up into the chamber 56 and into exhaust conduit 70, the delayed termination of air movement assuring this, and the yarn end is thereby engaged by the yarn tensioning device and retained for subsequent reinsertion. That is, at the end of the yarn change, the end of the Withdrawn yarn assumes the position formerly held by the newly inserted yarn, prior to the yarn change. As will be evident, the operation of the device is not limited to two yarns, but three or four or more yarns may be handled with equal facility. A simplified embodiment of the invention, which utilizes suction effect as the sole means of holding and tensioning the yarns over the dial cap, is illustrated in FIGURE 8. In this embodiment, the yarn tensioning device indicated generally as 1%) is disposed at the position of the yarn tensioning device 44 described in connection with the previous embodiment. The yarn tensioning device 1% comprises a conduit 192, which may be a short length of copper tubing, having a side branch 194 extending therefrom, the sfde branch opening a short distance, perhaps A or A; inch, above the dial cap at a point angularly spaced approximately from the knitting station in the direction of cylinder rotation, and situated adjacent the periphery of the dial cap. The conduit 19?. and its side branch 194 may be suitably mounted and positioned by means of a bracket 1%, mounted on and extending from the hearingbr'acket 198 or the machine. The flexible air" pressure'hose 166 is joined to the inlet end of the Conduit 192, as. shown, and adjacent the juncture of branch 194, a nozzle 20!) is formed in the conduit 192, this nozzle terminating adjacent the juncture of the branch and being d rected toward the outlet end of the conduit 192. ,As will be understood, when a high velocity air streamis passed through the conduit 192 from the inlet to the outlet'e'nd thereof, the noizle 200 and side branch 394 function as an aspirator, causing a suction in'the branch 194 and inducing an air flow into the open end thereof.

The yarn severing means 100 of the previously described embodiment maybe utilized without change, and the pneumatic system ma "be in all respects as previously described. In this embodiment, however, the actuating rod 84 of the machine is not utilized and the lever 78 and associated elements are omitted.

Function and operation of the FIGURES embodiment will be des'cribedin c'onnection with FIGURES 9 and 10. Prior to a yarn change, one yarn finger such as 26C is down in active position, feeding its yarn 30C directly into the'needles 32. The inactive yarn fingers 26D and 26E are in up position, and yarns extend therefrom (see FIG- URE 8) under guide tongue 42, into the open lower end of side branch 194, andiinto the outlet portion of the conduit 192. Immediately prior to the yarn change, the resistance wire 106 is heated as previously described. Next, 01' substantially simultaneously, a jog of the main drum effects rotation of hell crank 176 (FIGURE 11), and actuating link 168 is displaced to open the air valve 162. High pressure air thereupon flows through reservoir 164, flexible hose 166, and conduit 192 of the yarn tensioning device. The airfflow through the conduit 192, as previously indicated, creates ,a vacuum in the side branch 194 and elfects a high velocity airflow through the outis: end of the conduit 192, which combine to exert effective tension on the free ends of the inactive yarns 30D'and 30E. 7 p 7 Assuming the yarn socis'to heire laeedin the knitting by the yarn 30D, substantially simultaneously the yarn finger 26D is dropped to active position, whereupon its yarn is engaged by the needles 32 and drawn into the knitting. The 'tensionexerted by the tensioning' device 190 Oil the inactive insure that it is taken by the intended needles, and that a positive yarn lap results. Referring to FIGURE 9, the newly inserted yarn 39Dis carried by the first needle to knit initially'to the position 30D, at which point the arn is drawn partian out from u'nder'th'e vguide tongue .42. Air movement through the eondui in takes up the slack in the yarn end, and maintains effective tension thereon. v v

'The yarnen'd' is carried subsequently by the first needle to knit 'to the position 30D", a which time the first needle to knit the newly inserted yarn passes closely adjacent the side branch 194, and the air movement through the conduit 192 functions as previously described to take up the slack in the tree yarn end and maintain 'efiective tensioning thereof. Subsequently the end of the newly inserted yarn is carried by the first needle to knit to the'position 3G In the course of movement from the position 30D" to the position 30D, the yarn end is extended with respectto the side branch 194, and drawn out therefrom, against the restraining influence of the air flow. These factors'combine to'maintain effective tension on the yarn end as it is guided by the guide channel 112 into contact with the leading section 110 of the resistance wire 106, as thatsevering of the yarn by the resistance wire 106 close to the fabric is insured. As in the preyious embodiment, the yarn tensioning device 198 is efifective to manipulate and tension the yarn 'for severing within about'i /i' inch of the fabric. The severed end is carried away through the outlet portion i of conduit 192.

A'brief interval of time after the yarn 39D has been in- "serted' into'the knitting, perhaps 8'or I needles later, the

. 8 a formerly active yarn 3M3 is withdrawn from the knitting" by elevation of its yarn linger 26C. Upon withdrawal of the yarn 30C from the knitting, the yarn end is carried by the last needle to knit this yarn initially to the position sec (see FIGURE 10) at which position the yarn is drawn under the guide tongue 42. The yarn 39C is carried thereafter by the last needle to knit to the position 36C", at which position it is well under the guide tongue 42, and extends as well under the end of side branch 194 of the yarn tensioning device. The suction in the side branch 194 and the resultant air flow thereinto tend to draw the yarn 36C up into the side branch 194-, so that a bight of the yarn extending from the yarn finget to the last needle to knit is drawn up against the lower end of the side branch and into the interior thereof. This engagement of a light of the yarn length takes up all slack therein, and applies effective tension thereto.

The last needle to knit the previously active yarn subsequently carries the yarn to the position 39C, and into contact with the resistance wire 106. 'In progressing from the position 3iiC to the position 311C, the yarn 30Cis eh't'e'nded with respect to its ytilh fin er 26C, but a travelling bight thereof remains engaged in the branch 194 of the tensioning device by the previously described suction effect, whereby the yarn end assumes the angled position illustrated in FIGURE 10, both segments thereof being efiectivelytensioned by the tensioning device. As the yarn 363C is guided into contact'with the leading section of the resistance wire 106, it is severed as previously described, close to the fabric so as to leave an end extending therefrom only about A1. inch long. As soon as the yarn 36C is severed from the fabric, the free end extending from the yarn finger 26C is immediately drawn up into the side branch 194 and the outlet section of the conduit 192, whereby it is engaged and retained for subsequent reinsertion into the knitting. The final dispositi'on of the end of the now inactive yarn 30C is as illustrated in FIGURE 8. As in the previous case, the reservoir 164' of the pneumatic system insures that air flow through the conduit I92 persists until the newlywithdrawn yarn has been severed and etiec'tivelycng'ag'ed. It will'be recognized that the yarn t'ensioning device 190 eliminates all moving parts from the dial cap.

The bypass switch of the electrical circuit is useful for testing the resistance wire 106, and for other purposes. The resistance wire maybe tested when the machine is at rest, by closing the bypass switch, and manually elevating the arm 136 to permit switch 122 'to'close. It will be evident that chain lugs 146 not corresponding to yarn changes enect minor heating of the resistance wire 16 in passing under the pawl 142. This occasional minor heating is not detrimental, and may be eliminated if desired by incorporation of another" switch, operated by a main drum cam, into the electrical circuit.

The yarn'tensioning device of the inventionis particu- Iarly effective with the novel yarn severing means disclosed. It will be apparent, however, that the yarn ten sioning device may be employed with other means to sever the yarn, such as a high speed reciprocating shear. It will thus be seen that there has been'provide'd by this invention apparatus and methodsin'which the various objects hereinbefore'set forth, together with many practical advantages, are successfully achieved. As various possible embodiments may be made of the several features .of the above invention, all without departing from the scope thereof, it is to be understood that all matter hereinhefore set forth or shown in the accompanying drawings is to be interpreted as illustrative, and not in a limiting sense.

We claim:

1. In a'circular knitting machine having a rotary cylin der with independent needles, a dial cap mountedfa'd- .jacent the top of said cylinder anda' g'r'oup of individually retractable interchangeable yarn feeds, yarn 'tensioning above said dial cap at a-point angularlyspaced fromsaid yarn feed group in the direction of cylinder rotation, means for inducing air flow into said open end, and means for displacing said open end into and out of clamping relationship with said dial cap.

2. In a circular knitting machine having a rotary cylinder with independent needles, a dial cap mounted adjacent the top of said cylinder, a group of individually retractable interchangeable yarn feeds, and a timing drum controlling the movement of said yarn feeds, yarn tensioning means comprising a conduit having an open end disposed above said dial cap at a point angularly spaced from said yarn feed group in the direction of cylinder rotation, means for inducing air flow into said open end, and means actuated by said drum for displacing said open end into and out of clamping relationship with said dial can.

3. In a circular knitting machine having a rotary cy1inder with independent needles, a dial cap mounted adjacent the top of said cylinder, and a group of individually retractable interchangeable yarn feeds, yarn tensioning means comprising a housing disposed above said dial cap at a point angularly spaced from said yarn feed group, a bore extending vertically through said housing, a sleeve slidably mounted in said bore, the upper end of said sleeve being closed, said sleeve having diametrically opposed vertically extended slots in the walls thereof, a conduit member extending through said housing and one of said slots into the interior of said sleeve, a second conduit member extending through said housing in alignment with the other of said slots, and means for vertically displacing said sleeve to move its lower end into and out of clamping relationship with said dial.

4. A circular knitting machine as defined in claim 3, including a timing drum controlling the movement of said yarn feeds, said timing drum also actuating said sleeve displacing means.

References Cited in the file of this patent UNITED STATES PATENTS Shoaf Oct. 31, 1961 

1. IN A CIRCULAR KNITTING MACHINE HAVING A ROTARY CYLINDER WITH INDEPENDENT NEEDLES, A DIAL CAP MOUNTED ADJACENT THE TOP OF SAID CYLINDER, AND A GROUP OF INDIVIDUALLY RETRACTABLE INTERCHANGEABLE YARN FEEDS, YARN TENSIONING MEANS COMPRISING A CONDUIT HAVING AN OPEN END DISPOSED ABOVE SAID DIAL CAP AT A POINT ANGULARLY SPACED FROM SAID YARN FEED GROUP IN THE DIRECTION OF CYLINDER ROTATION, MEANS FOR INDUCING AIR FLOW INTO SAID OPEN END, AND 